It is known that the wheels of vehicles are generally made up of a cylindrical metal rim having, at the axial extremities, annular flanges between which the beads of the tyre are interlocked.
These wheels require frequent balancing operations which consist in applying to the rim of the wheel small weights, made of lead or other material, suitable for offsetting the irregular distribution of the tire weights.
To perform such operation, balancing machines are commonly used having a rotating spindle, so-called “balancing spindle”, on which the wheel to be balanced must be positioned integral in order to start it rotating and determine its unbalance.
The balancing spindle is arranged horizontally at a preset distance from the ground and the wheel is normally fitted on it manually by an operator who lifts the wheel up by hand and positions it coaxially on the balancing spindle.
Such manual operations are often uncomfortable and tiring for the operator, particularly when the wheel to be balanced is very heavy and large.
To make the operator's task easier, lifting devices made up of a platform which is mobile both along a vertical direction and along a direction parallel with the balancing spindle may be utilized.
The wheel to be balanced is allowed to roll onto the platform positioned near the ground and here is kept in vertical position, meaning balanced on the tread and with its rolling axis arranged horizontally.
To maintain the vertical position, the operator keeps one or both hands on the wheel, thereby preventing the wheel from falling; alternatively, the platform can, if necessary, be equipped with a locking vice which is tightened on the opposite sides of the wheel, restricting any possible movement.
In the vertical position, the wheel is lifted up to the height of the balancing spindle by means of the operation of a hydraulic and/or pneumatic actuator that causes the platform to elevate, and is then fitted coaxially on the balancing spindle by means of the horizontal movement of the platform itself.
Once fitted, the wheel is fastened on the balancing spindle by means of specific centering and fastening means and, subsequently, is rotated to calculate its unbalance.
The wheel unbalance measurement is read by special electronic or electro-mechanical devices, such as force transducers fitted along the balancing spindle.
To the unbalance measurement are generally added other characteristic measurements, such as the measurement of the roundness of the wheel, the eccentricity of the wheel, the amount of wear of the tread, etc., normally done by means of contact-free measurement sensors (laser, ultrasounds or the like), fitted on the machine frame and substantially turned towards the balancing spindle.
The balancing machines of traditional type are, however, susceptible to further upgrading, aimed at increasing their functionality and efficiency of use.
In this respect, the fact is emphasized that, including in the presence of a lifting platform, the phase of fitting the wheel on the balancing spindle is not always practical and easy, taking into account the need for the operator to correctly align the balancing spindle and the center of the wheel before coupling these together.
This operation is, in fact, performed visually by the operator, who operates the hydraulic and/or pneumatic actuator for lifting the platform until he/she considers the balancing spindle and the centre of the wheel to be aligned.
This operation, therefore, inconveniently keeps the operator engaged for a certain amount of time and is unfortunately subject to the sensitivity and the experience of the operator, and to possible alignment errors.
In this respect, any alignment errors by the operator make it necessary to repeat the operation and, therefore, determine a further extension of execution times, with the consequent increase in labour costs and total costs for the end customer.